utils: fix encoding of EF.MSISDN

The encoding of EF.MSISDN is a bit unstrutured. The encoder function
does not return a valid result since it lacks the parameters
Capability/Configuration2 Record Identifier and Extension5 Record
Identifier, which are mandatory but can be set to 0xFF. Also the
encoder gets its input from pySim-shell, so it should have some
more input validation, especially when the user encodes an empty
string. The encoder and decoder function also do not have unit-tests.

Since the encoder now adds the missing two bytes by isself this does
not have to be done manually anymore, so cards.py needs to be
re-aligned.

For pySim-shell.py the encoder is used from ts_51_011.py. Unfortunately
it is used wrongly there. The optional Alpha Identifier is required
here as well.

Related: OS#4963
Change-Id: Iee5369b3e3ba7fa1155facc8fa824bc60e33b55b
diff --git a/pySim/cards.py b/pySim/cards.py
index 9a19eed..719bf0c 100644
--- a/pySim/cards.py
+++ b/pySim/cards.py
@@ -963,7 +963,7 @@
 		# TODO: Extension1 Record Identifier
 		if p.get('msisdn') is not None:
 			msisdn = enc_msisdn(p['msisdn'])
-			data = 'ff' * 20 + msisdn + 'ff' * 2
+			data = 'ff' * 20 + msisdn
 
 			r = self._scc.select_path(['3f00', '7f10'])
 			data, sw = self._scc.update_record('6F40', 1, data, force_len=True)
@@ -1356,7 +1356,7 @@
 		# TODO: Extension1 Record Identifier
 		if p.get('msisdn') is not None:
 			msisdn = enc_msisdn(p['msisdn'])
-			content = 'ff' * 20 + msisdn + 'ff' * 2
+			content = 'ff' * 20 + msisdn
 
 			r = self._scc.select_path(['3f00', '7f10'])
 			data, sw = self._scc.update_record('6F40', 1, content, force_len=True)